1. Field of the Invention
The present invention relates to a surface texture measurement apparatus that measures the texture of a measurement target surface on the basis of the displacement of the contact part of a stylus. The displacement is detected in a state in which the contact part of the stylus is in contact with the measurement target surface. In addition, the invention relates to a roundness measuring apparatus.
2. Description of the Related Art
A roundness measuring apparatus that is used for acquiring various kinds of data related to the roundness of a measurement target object such as a cylindrical column, a circular cylinder, or the like is known well. The roundness data includes, for example, data regarding circularity, concentricity, and coaxiality. A roundness measuring apparatus measures and calculates the roundness of a measurement target object as follows. A measurement target object, which is an object to be measured, is placed on a turntable. The surface position of the measurement target object is detected by means of a contact type stylus while the turntable is rotated. Data regarding the surface position of the measurement target object being rotated thereon is acquired for measuring and calculating the roundness of the measurement target object (refer to Japanese Unexamined Patent Application Publication Nos. 2007-71726 and H6-300505).
Especially when a measurement target surface is soft, an excessive pressing force of a stylus that is applied onto the measurement target surface will have adverse effects on the result of measurement. For example, measurement values could vary widely. As a conventional solution for avoiding the above influence, an apparatus for measuring surface texture such as a roundness measuring apparatus that is provided with a measuring force adjustment mechanism is used. The measuring force adjustment mechanism is capable of adjusting the measuring force of a detector depending on the material of a measurement target object or the like. FIG. 6 is a diagram that schematically illustrates an example of the structure of a measuring force adjustment mechanism of a roundness measuring apparatus according to related art. As illustrated in FIG. 6, a wire spring 160 is used as a component of the measuring force adjustment mechanism. One end of the wire spring 160 is connected to a sliding switch 190. The other end of the wire spring 160 is connected to the base end of a stylus 140. When a user moves the sliding switch 190 manually, the degree of bending of the wire spring 160 changes. By this means, the user can adjust the measuring force of the stylus 140 manually.
However, to change a measuring force by means of such a conventional measuring force adjustment mechanism, a user has to manually operate a sliding switch as explained above. When the user desires to change a measuring force during measurement, it is necessary to temporarily suspend a measurement program, manually change the measuring force, and thereafter restart the measurement program. To motorize a structure for changing the degree of bending of a wire spring, it is necessary to provide a dedicated driver, a controlling scale, and the like as additional components. These dedicated driver and controlling scale that are added to an existing detector will increase the size of the detector. In addition, such a structure is disadvantageous in terms of cost.